Substrate processing apparatus and substrate processing method

ABSTRACT

When a substrate W is processed, a cover member covers a peripheral portion of the upper surface of the substrate held by the substrate holding unit, and a central portion of the substrate located at an inner position than the peripheral portion in a radial direction is exposed without being covered by the cover member. A gap is formed between the lower surface of the cover member and the peripheral portion of the upper surface of the substrate held by the substrate holding unit. When the interior space of the cup is exhausted, a gas present above the interior space of the cup is introduced from a space enclosed by the internal peripheral surface of the cover member through the gap into the interior space of the cup.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority from Japanese Patent Application No. 2012-235982, filed on Oct. 25, 2012 with the Japan Patent Office, the disclosure of which is incorporated herein in its entirety by reference.

TECHNICAL FIELD

The present disclosure relates to a substrate processing apparatus and a substrate processing method for processing a peripheral portion of a rotating substrate by supplying a processing liquid to the peripheral portion.

BACKGROUND

A manufacturing process of semiconductor devices includes a peripheral portion cleaning process of removing an unnecessary film or contaminants from a peripheral portion of a semiconductor wafer (hereinafter, simply referred to as a “wafer”), which is a target substrate, by supplying a processing liquid such as a chemical liquid to the peripheral portion of the wafer while rotating the wafer. Such a cleaning is called as a bevel cleaning or an edge cleaning.

Japanese Patent Application Laid-Open No. 2012-84856 discloses a liquid processing apparatus for cleaning a peripheral portion. The liquid processing apparatus includes a vacuum chuck configured to hold a wafer horizontally and rotate the wafer around a vertical axis, a nozzle configured to eject a chemical liquid onto the peripheral portion of the rotating wafer, a cup configured to surrounds the periphery of the wafer to receive a processing liquid scattered from the wafer, and a disc-shaped cover member configured to the upper side of the upper surface of the wafer and seal the upper surface of the cup in close proximity to the upper surface. A chimney-shaped intake pipe is provided from the central portion of the upper surface of the cover member. Further, the cover member is provided with a protrusion that protrudes downward at a position just above the peripheral portion of the wafer. Since the interior space of the cup is at a negative pressure by being evacuated, a down flow of clean air flowing through a housing is sucked from the intake pipe, flows through a space between the upper surface of the wafer and the lower surface of the cover member towards the peripheral portion of the wafer, and flows through a narrow gap formed between the protruding portion of the cover member and the upper surface of the wafer into the inside of the cup. By this gas flow, the mist of the chemical liquid scattered towards the outside of the wafer is prevented from being attached again to the upper surface of the wafer and contaminating the upper surface of the wafer (device forming surface).

However, since the cover member of Japanese Patent Application Laid-Open No. 2012-84856 covers the entire surface of the wafer, the flow resistance from the inlet of the intake pipe to the cup is large. As a result, unless the interior space of the cup is exhausted strongly, a gas flow with a sufficient flow rate may not be obtained at the outlet of the narrow gap.

SUMMARY

The present disclosure provides a substrate processing apparatus including: a substrate holding unit configured to hold a substrate horizontally; a rotation driving mechanism configured to rotate the substrate holding unit around a vertical axis; a processing liquid nozzle configured to supply a processing liquid to a peripheral portion of the substrate held by the substrate holding unit; a cup configured to receive the processing liquid scattered outwardly from the substrate, the cup having an upper opening and enclosing the periphery of the substrate held by the substrate holding unit; an exhaust port configured to exhaust the interior space of the cup; and a ring-shaped cover member having a lower surface and an internal peripheral surface, in which the cover member covers the peripheral portion of the upper surface of the substrate held by the substrate holding unit, a central portion of the substrate located at an inner position than the peripheral portion in a radial direction is exposed without being covered by the cover member, a gap is formed between the lower surface of the cover member and the peripheral portion of the upper surface of the substrate held by the substrate holding unit, and when the interior space of the cup is exhausted, a gas present above the interior space of the cup is introduced from a space enclosed by the internal peripheral surface of the cover member through the gap into the interior space of the cup.

The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross-sectional side view of a liquid processing apparatus according to an exemplary embodiment of the present disclosure.

FIG. 2 is a plan view illustrating a cover member, an elevation mechanism and a supplying unit of the liquid processing apparatus illustrated in FIG. 1.

FIG. 3 is a cross-sectional view illustrating a region in the vicinity of an external periphery of the right wafer in FIG. 1 in detail in an enlarged scale.

FIG. 4A and FIG. 4B are explanatory views of a nozzle.

FIG. 5A and FIG. 5B are views illustrating the flows of a processing fluid inside and in the vicinity of a cup. FIG. 5A is a view illustrating flows of liquids, and FIG. 5B is a view illustrating flows of air current and mist entrained in the air current.

DETAILED DESCRIPTION

In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. The illustrative embodiments described in the detailed description, drawing, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here.

The present disclosure provides a technique capable of effectively suppressing a processing liquid supplied to a substrate from being scattered and adhered again onto the substrate, while reducing a load on an exhaust apparatus that exhaust a cup.

The present disclosure provides a substrate processing apparatus including: a substrate holding unit configured to hold a substrate horizontally; a rotation driving mechanism configured to rotate the substrate holding unit around a vertical axis; a processing liquid nozzle configured to supply a processing liquid to a peripheral portion of the substrate held by the substrate holding unit; a cup configured to receive the processing liquid scattered outwardly from the substrate, the cup having an upper opening and enclosing the periphery of the substrate held by the substrate holding unit; an exhaust port configured to exhaust the interior space of the cup; and a ring-shaped cover member having a lower surface and an internal peripheral surface, in which the cover member covers the peripheral portion of the upper surface of the substrate held by the substrate holding unit, a central portion of the substrate located at an inner position than the peripheral portion in a radial direction is exposed without being covered by the cover member, a gap is formed between the lower surface of the cover member and the peripheral portion of the upper surface of the substrate held by the substrate holding unit, and when the interior space of the cup is exhausted, a gas present above the interior space of the cup is introduced from a space enclosed by the internal peripheral surface of the cover member through the gap into the interior space of the cup.

In the above-described substrate processing apparatus, an internal diameter of the lower portion of the internal peripheral surface of the cover member becomes larger as it goes downwardly. Further, a lower end of the internal peripheral portion and an internal peripheral portion of the lower surface in the cover member are connected to each other so as to be a curved surface.

In the above-described substrate processing apparatus, an internal periphery of the lower surface of the cover member is located at an inner position than an external peripheral end of the substrate held by the substrate holding unit, and an external periphery of the lower surface of the cover member is located at an outer position than an external periphery of the substrate held by the substrate holding unit. Further, the internal periphery of the lower surface of the cover member is located at an inner position than an internal periphery of the peripheral portion of the substrate held by the substrate holding unit.

In the above-described substrate processing apparatus, an opening area of the gap is larger than that of the exhaust port.

In the above-described substrate processing apparatus, the cup has an upper opening into which the lower portion of the cover member is inserted, and a wall that defines the upper opening of the cup is provided with a folded portion that extends downwardly.

The substrate processing apparatus further includes a moving mechanism configured to move the cover member between a processing position that comes close to the upper surface of the substrate held by the substrate holding unit and a retreat position apart from the substrate.

Further, the present disclosure provides a substrate processing method including: holding a substrate horizontally in a state where the periphery of the substrate is enclosed by a cup, and an upper side of the substrate is covered by a ring-shaped cover member; and performing a liquid processing on the substrate by supplying a processing liquid to a peripheral portion of the substrate in a state where the interior space of the cup is exhausted and the substrate is rotated around a vertical axis, in which, when the liquid processing is performed on the substrate, the cover member covers the peripheral portion of an upper surface of the substrate held by the substrate holding unit, a central portion of the substrate located at an inner position than the peripheral portion in a radial direction is exposed without being covered by the cover member, a gap is formed between a lower surface of the cover member and the peripheral portion of the upper surface of the substrate held by the substrate holding unit, and when the interior space of the cup is exhausted, a gas present above the interior space of the cup is introduced from a space enclosed by the internal peripheral surface of the cover member through the gap into the interior space of the cup.

In the substrate processing method, the gas flows horizontally and outwardly through the gap between the lower surface of the cover member and the peripheral portion of the upper surface of the substrate.

According to the present disclosure, since a ring-shaped cover member is used cover a peripheral portion of a substrate, flow resistance may be reduced in a fluid path (gap) formed between a lower surface of the cover member and an upper surface of the substrate, thereby reducing a load of the exhaust apparatus that exhausts a cup. Further, by a gas flowed outwardly from the substrate through the gap formed between the lower surface of the ring-shaped cover member and the upper surface of the substrate, a processing liquid supplied to a substrate may be prevented effectively from being scattered and adhered again onto the substrate.

An exemplary embodiment of a substrate processing apparatus of the present disclosure will be described with respect to a liquid apparatus that supplies a hydrofluoric acid (HF) solution, which is a chemical liquid, to a surface of a wafer W, which is a disc-shaped substrate where semiconductor devices are formed, to remove an unnecessary film formed on the peripheral portion of the wafer W.

As illustrated in FIG. 1 and FIG. 2, a liquid processing apparatus 1 includes a wafer holding unit 3 configured to hold a wafer W rotatably around a vertical axis in a horizontal posture; a cup 2 configured to enclose the periphery of the wafer W held on the wafer holding unit 3 and receives a processing liquid scattered from the wafer W; a cover member 5 configured to cover a peripheral portion of an upper surface of the wafer W held in the wafer holding unit 3; a elevation mechanism (moving mechanism) 6 configured to move up and down the cover member 5; and a processing fluid supplying unit 7 configured to supply a processing fluid to the wafer W held in the wafer holding unit 3.

The constitutional elements of the liquid processing apparatus as described above such as, for example, the cup 2, the wafer holding unit 3, and the cover member 5, are accommodated in one housing 11. A clean air introducing unit 14 configured to introduce clean air from the outside is provided in the vicinity of the ceiling of the housing 11. Further, an exhaust port 15 configured to exhaust the atmosphere in the housing 11 is provided in the vicinity of the bottom surface of the housing 11. As a result, downflow of the clean air is formed in the housing 11, flowing from the upper portion of the housing 11 towards the lower portion. A carrying-in/out port 13 is provided at a side wall which is opened/closed by a shutter 12. A transportation arm (not illustrated) provided outside the housing 11 may pass through the carrying-in/out port 13 in a state where the wafer W is held thereon.

The wafer holding unit 3 is constituted with a disc-shaped vacuum chuck, and the upper surface of the wafer holding unit 3 is formed as a wafer adsorption surface 31. A suction port 32 is opened at the central portion of the wafer adsorption surface 31. A hollow cylindrical rotation shaft 44 extends vertically from the central portion of the lower surface of the wafer holding unit 3. A suction conduit (not illustrated) passes through the interior space of the rotation shaft 44 and is connected to the suction port 32. The suction conduit is connected to a vacuum pump 42 in the outside of the housing 11. When the vacuum pump 42 is driven, the wafer W may be sucked by the wafer holding unit 3.

The rotation shaft 44 is supported in a bearing casing 45 in which a bearing 451 is embedded, and the bearing casing 45 is supported on the bottom surface of the housing 11. The rotation shaft 44 may be rotated at a predetermined speed by a rotation driving mechanism 46 including a driven pulley 461 on the rotation shaft 44, a driving pulley 462 on a rotation shaft of a driving motor 463, and a driving belt 464 extending between the driven pulley 461 and the driving pulley 462.

As illustrated in FIG. 3, the cup 2 is a bottomed annular member configured to enclose the external periphery of the wafer holding unit 3. The cup 2 serves to receive and recover the chemical liquid scattered outwardly from the wafer W after the chemical liquid is supplied to the wafer W, and eject the chemical liquid to the outside.

A relatively small gap (e.g., having a height of about 2 mm to 3 mm) is formed between the lower surface of the wafer W held by the wafer holding unit 3 and the upper surface 211 of an internal peripheral side portion 21 of the cup 2 facing the lower surface of the wafer W. Two gas ejection ports 212, 213 are opened on the upper surface 211 which is opposite to the wafer W. The two gas ejection ports 212, 213 extend continuously along the concentric large-diameter circumference and small-diameter circumference, respectively, and eject hot N₂ gas (heated nitrogen gas) towards the lower surface of the wafer W in a radially outward and obliquely upward direction.

The N₂ gas is supplied from one or a plurality of gas introduction lines 214 (only one illustrated in the figure) formed in the inside of the internal peripheral side portion 21 of the cup 2 to an annular gas diffusion space 215. The N₂ gas flows through the gas diffusion space 215 while spreading in the circumferential direction, and is ejected from the gas ejection ports 212, 213. A heater 216 is provided in the vicinity of the gas diffusion space 215. Accordingly, the N₂ gas is heated when the flowing through the gas diffusion space 215, and then, ejected from the gas ejection ports 212, 213. The N₂ gas ejected from the gas ejection port 213, which is disposed radially outside, heats up the peripheral portion of the wafer W, which is a part to be processed, to promote reaction with the chemical liquid. Also, the N₂ gas suppresses the mist of the processing liquid, which has been ejected towards the front surface (upper surface) of the wafer W and then scattered, from coming back to the back surface (lower surface) of the wafer. The N₂ gas ejected from the gas ejection port 212, which is disposed radially inside, suppresses deformation of the wafer W. The deformation may be caused because only the peripheral portion of the wafer W may be heated unless the gas ejection port 212 is provided and a negative pressure is generated near the lower surface of the wafer W at the central side of the wafer W.

In an external peripheral portion 21 of the cup 2, two top-opened annular recesses 241, 242 are formed along the peripheral direction of the cup 2. The recesses 241, 242 are partitioned from each other by an annular separation wall 243. A drain path 244 is connected to the bottom of the outer recess 241. Further, an exhaust port 247 is provided in the bottom of the inner recess 242, and an exhaust path 245 is connected to the exhaust port 247. An exhaust apparatus 246 such as, for example, an ejector or a vacuum pump, is connected to the exhaust path 245. During the operation of the liquid processing apparatus 1, the interior space of the cup 2 is normally exhausted to maintain the pressure in the inside of the inner recess 242 lower than the pressure in the inside of the housing 11 in the outside of the cup 2.

A ring-shaped guide plate 25 extends from the external periphery of the internal peripheral portion 21 of the cup 2 (a downward position of the peripheral portion of the wafer W) towards the radial outside. The guide plate 25 is inclined to become lower as it goes in the radial direction. The guide plate 25 covers the entire inner recess 242 and the upside of the internal peripheral portion of the outer recess 241. The front end 251 of the guide plate 25 (the radial external peripheral portion) is bent downwardly and enters into the outer recess 241.

Further, an external peripheral wall 26 which is continuous with an outer wall surface of the outer recess 241 is provided in the external periphery of the external peripheral portion 24 of the cup 2. The outer peripheral wall 26 receives fluid (e.g., liquid droplets, gas or a mixture thereof) scattered outwardly from the wafer W by the internal peripheral surface thereof, and guides the fluid towards the outer recess 241. The external peripheral wall 26 includes a fluid receiving surface 261 in the inside thereof which is inclined at an angle of 25° to 30° with respect to the horizontal surface to be lowered towards the radial outside, and a folded portion 262 that extends downwardly from the upper end of the fluid receiving surface 261. In the example as illustrated, the fluid receiving surface 261 formed as an inclined surface is connected via a horizontal surface 263 to the folded portion 262. However, a curved surface may be provided instead of the horizontal surface 263, or the folded portion 262 may be connected directly to the upper end of the fluid receiving surface 261 without the horizontal surface 263. An exhaust fluid path 27 that allows gas (e.g., air or N₂ gas) and liquid droplets scattered from the wafer W to flow is formed between an upper surface 252 of the guide plate 25 and the fluid receiving surface 261. Meanwhile, the upper opening of the cup 2 is defined by the internal peripheral surface of the folded portion 262, but the opening diameter of the upper opening is slightly larger than the diameter of the wafer W.

A mixed fluid of the gas and the liquid droplets introduced through the exhaust fluid path 27 into the outer recess 241 flows between the guide plate 25 and the separation wall 243 and is introduced into the inner recess 242. When the mixed fluid passes between the guide plate 25 and the separation wall 243, the flow direction of the mixed fluid is sharply turned. Accordingly, the liquid (droplets) included in the mixed fluid is separated from the fluid by collision with the front end 251 of the guide plate 25 or the separation wall 243, introduced into the outer recess 241 along the lower surface of the guide plate 25 or the surface of the separation wall 243, and discharged from the drain path 244. The fluid in which liquid droplets have been removed is introduced into the inner recess 242, and then, discharged from the exhaust path 245.

The cover member 5 is a ring-shaped member disposed to face the peripheral portion of the upper surface of the wafer W when the processing is performed. As described below, the cover member 5 rectifies gas that flows near the peripheral portion of the upper surface of the wafer W and is drawn into the cup 2, and increases a flow rate of the gas, thereby suppressing the processing liquid scattered from the wafer W from being adhered again onto the upper surface of the wafer W.

As illustrated in FIG. 3, the cover member 5 includes an internal peripheral surface 51, and a horizontal lower surface 52 facing the wafer W. The internal peripheral surface 51 has an upper side portion 511 that extends vertically and a lower side portion 512 that is inclined to be directed towards the radial outside as it comes close to the wafer W. A vertical gap G is formed between the lower side portion 512 and the upper surface of the wafer W. An external periphery 521 of the cover member 5 is located at an outer position than an external peripheral end We of the wafer W in a radial direction. Further, an internal periphery 53 of the lower surface 52 of the cover member 5 is located at an inner position than an internal periphery Wi of a peripheral portion Wp of the wafer W in the radial direction. Accordingly, an air current passing through the gap G flows horizontally forwards the outside of the wafer W, at least in the peripheral portion Wp of the wafer W. Here, the “peripheral portion Wp of the wafer W” refers to an annular region in which a device is not formed. The “internal periphery Wi of the peripheral portion Wp of the wafer W refers to a circumscribed circle of a device forming region, that is, a circle which takes the center of the wafer W as a center and has a minimum radius determined so that the device forming region is not included at all in the outside of this circle) to the external peripheral end We of the wafer W. A radial width of the peripheral portion Wp of the wafer W, that is, a radial distance from the external peripheral end We to the internal periphery Wi of the peripheral portion Wp of the wafer W is, for example, about 3 mm.

FIG. 2 is a plan view illustrating a state where the wafer W is held on the wafer holding unit 3 and the cover member 5 is located at a processing position. In FIG. 2, the external peripheral end (edge) We of the wafer which is covered with the cover member 5 is illustrated by the dashed line. In addition, the internal periphery of the cover member 5 is represented by the reference numeral 5 e. As such, since the central portion of the cover member 5 is opened, the flow resistance of the fluid path formed between the lower end of the cover member and the wafer W becomes smaller as compared with the disc-shaped cover member that covers the substantially entire surface of the wafer in the related art. Accordingly, even if the exhaust capability to exhaust the interior space of the cup 2 is low, sufficient exhaust may be performed. Further, since most of the upper surface of the wafer W excluding the peripheral portion is not covered by the cover member 5, the surface of the wafer W may be monitored during the processing, for example, by providing a camera in the housing 11. Further, the surface of the wafer W may also be checked during the processing by providing a transparent window in the housing 11.

As illustrated in FIGS. 1 and 2, the elevation mechanism 6 configured to move up and down the cover member 5 includes a plurality (four in this example) of sliders 61 fixed to a support 58 that supports the cover member 5, and guide pillars 62 that penetrate the respective sliders 61 and extend vertically. A linear actuator, for example, a rod 631 of a cylinder motor 63 is connected to each of the respective sliders 61. When the cylinder motor 63 is driven, the slider 61 is moved up and down along the guide pillar 62, and thus, is capable of moving up and down the cover member 5. The cup 2 is supported by a lifter 65 that constitutes a part of a cup elevation mechanism (details are not illustrated). As the lifter 65 is moved down from the state illustrated in FIG. 1, the cup 2 descends, and thus, the wafer W may be transferred between a transportation arm of a wafer transportation mechanism (not illustrated) and the wafer holding unit 3.

Next, referring to FIGS. 1, 2 and 4, the processing fluid supplying unit 7 will be described. Particularly, as clearly illustrated in FIG. 2, the processing fluid supplying unit 7 includes a chemical liquid nozzle 71 configured to eject a chemical liquid (HF in this example), a rinse nozzle 72 configured to eject a rinse liquid (deionized water (DIW) in this example), and a gas nozzle 73 configured to eject a gas for drying (N₂ gas in this example). The chemical liquid nozzle 71, a rinse nozzle 72 and a gas nozzle 73 are attached to a common nozzle holder 74. The nozzle holder 74 is attached to a linear actuator, for example, a rod 751 of a cylinder motor 75, which is in turn attached to the support 58 configured to support the cover member 5. When the cylinder motor 75 is driven, a supply position of the processing fluid onto the wafer W may be moved from the nozzles 71 to 73 in a radial direction of the wafer W.

As illustrated in FIGS. 2 and 4A, the nozzles 71 to 73 are accommodated in a recess 56 which is formed in the internal peripheral surface of the cover member 5. The respective nozzles 71 to 73 direct obliquely downwardly, as illustrated by an arrow A in FIG. 4B, and also, discharge the processing fluid such that the discharge direction represented by the arrow A has a component of a rotation direction Rw of the wafer. By doing this, it is possible to suppress generation of mist (liquid droplet generated due to collision of the processing liquid with the wafer W) which may be generated in a case where the processing fluid is liquid. The processing fluid is supplied from processing fluid supply mechanisms 711, 721, 731 as schematically illustrated in FIG. 2 to the respective nozzles 71 to 73. Each of the processing liquid supply mechanisms 711, 721, 731 may be constituted by a processing fluid supply source such as a tank, a pipeline that supplies the processing fluid from the processing fluid supply source to the nozzles, and a flow control device such as an opening/closing valve or a flow-rate adjusting valve installed in the pipeline.

Further, as illustrated in FIG. 3, in the internal peripheral side portion 21 of the cup 2, a plurality (only one illustrated in the figure) of processing liquid ejection ports 22 are formed at different positions with respect to the circumferential direction outside of the gas ejection port 213. The respective processing liquid ejection ports 22 eject the processing fluid outwardly from the wafer W and obliquely upwardly towards the peripheral portion of the lower surface of the wafer W. From at least one of the processing liquid ejection ports 22, the same chemical liquid as the chemical liquid ejected from the chemical liquid nozzle 71 may be ejected. Further, from at least another one of the processing liquid ejection ports 22, the same rinse liquid as the rinse liquid ejected from the rinse nozzle 72 may be ejected. As illustrated in FIG. 3, a process fluid supply mechanism 221 having the same configuration as the above-mentioned nozzles 71 to 73 is connected to each of the processing liquid ejection ports 22.

As schematically illustrated in FIG. 1, the liquid processing apparatus 1 includes a controller (control unit) 8 configured to integrally control the entire operations thereof. The controller 8 controls the operations of all functional parts (for example, the rotation driving mechanism 46, the elevation mechanism 6, the vacuum pump 42, and various processing fluid supply mechanisms). The controller 8 may be implemented using, for example, a general purpose computer as a hardware and a program (an apparatus control program and a processing recipe) to operate the computer as a software. The software may be stored in a storage medium such as, for example, a hard disc drive which is fixedly provided in the computer, or in a storage medium such as, for example, a CD-ROM, a DVD and a flash memory which are removably set in the computer. The storage medium is indicated by a reference numeral 81 in FIG. 1. A processor 82 accesses and executes a predetermined processing recipe from the storage medium 81 based on, for example, instructions from a user interface (not illustrated) as needed. As a result, each functional component of the liquid processing apparatus 1 is operated to perform a predetermined processing under the control of controller 8.

Next, description will be made on the operation of the liquid processing apparatus 1 performed under the control of the controller 8.

[Carry-in of Wafer]

First, the cover member 5 is disposed at a retreat position (upper position in FIG. 1), and the cup 2 is moved down by the lifter 65 of the cup elevation mechanism. Subsequently, a shutter 12 of the housing 11 is opened to allow a transportation arm (not illustrated) of an external wafer transportation mechanism (not illustrated) to enter the housing 11. Then, the wafer W held by the transportation arm is disposed just above the wafer holder 3. Subsequently, the transportation arm is moved down to a position lower than the upper surface of the wafer holder 3 to dispose the wafer W on the upper surface of the wafer holder 3. Next, the wafer W is adsorbed by the wafer holder 3. Thereafter, the empty transportation arm exits from the inside of the housing 11. Then, the cup 2 is moved up to return to the position as illustrated in FIG. 1, and the cover member 5 is moved down to the processing position as illustrated in FIG. 1. By the above-mentioned procedure, the carry-in of the wafer is completed, and is in a state as illustrated in FIG. 1.

[Chemical Liquid Processing]

Next, a chemical liquid processing is performed on the wafer W. The wafer W is rotated at a predetermined speed (e.g., 2,000 rpm). In addition, hot N₂ gas is ejected from the gas ejection ports 212, 213 of the cup 2 to heat the peripheral portion of the wafer W, which is a region to be processed, to a temperature suitable for the chemical liquid processing (e.g., 60° C.). Further, when performing a chemical processing which is not necessary to heat the wafer W, N₂ gas at normal temperature may be ejected without operating the heater 216. When the wafer W is heated sufficiently, the chemical liquid (HF) is supplied from the chemical liquid nozzle 71 to the peripheral portion of the upper surface (device forming surface) of the wafer W while rotating the wafer W, thereby removing any unnecessary film in the peripheral portion of the upper surface of the wafer. At the same time, the chemical liquid is supplied from the chemical liquid processing liquid ejection port 22 to the peripheral portion of the lower surface of the wafer W, thereby removing any unnecessary film in the peripheral portion of the lower surface of the wafer. The chemical liquid supplied to the upper and lower surfaces of the wafer W flows while spreading outwardly by centrifugal force, is flowed out of the wafer W together with the removed matters, and is recovered by the cup 2. Further, while the chemical liquid processing is performed, the chemical liquid nozzle 71, which is discharging the chemical liquid by driving the cylinder motor 75, may be reciprocated in the radial direction of the wafer W, thereby enhancing the uniformity of the processing.

[Rinse Processing]

After the chemical liquid processing is performed for a predetermined period of time, a rinse processing is subsequently performed by continuing the rotation of the wafer W and the ejection of N₂ gas from the gas ejection ports 212, 213, stopping the ejection of the chemical liquid from the chemical liquid nozzle 71 and the chemical liquid processing liquid ejection port 22, and supplying the rinse liquid (DIW) from the rinse nozzle 72 and the rinse liquid processing liquid ejection port 22 to the peripheral portion of the wafer W. By this rinse processing, the chemical liquid and any reaction products remained on the upper and lower surfaces of the wafer W are washed out.

[Dry Processing]

After the rinse processing is performed for a predetermined period of time, a dry processing is subsequently performed by continuing the rotation of the wafer W and the ejection of N₂ gas from the gas ejection ports 212, 213, stopping the ejection of the rinse liquid from the rinse nozzle 72 and the rinse liquid processing liquid ejection port 22, and supplying the gas for drying (N₂ gas) from the gas nozzle 73 and the rinse liquid processing liquid ejection port 22 to the peripheral portion of the wafer W. By the above procedure, a series of processings for the wafer W is completed.

[Carry-out of Wafer]

Thereafter, the cover member 5 is moved up to be disposed at the retreat position, and the cup 2 is moved down. Subsequently, the shutter 12 of the housing 11 is opened to allow the transportation arm (not illustrated) of the external wafer transportation mechanism (not illustrated) to enter the housing 11. Then, the empty transportation arm is disposed below the wafer W held by the wafer holder 3, and then, moved up to receive the wafer W from the wafer holder 3 in a state where the adsorption of the wafer W is stopped. Thereafter, the transportation arm holding the wafer W exits from the inside of the housing 11. By the above-mentioned procedure, a series of processings for one wafer is completed in the liquid processing apparatus.

Next, referring to FIGS. 3 to 5, descriptions will be made in detail on the flow of the fluid in the vicinity of the peripheral portion of the wafer and the configuration of the cup 2 and the cover member 5 related to the flow of the fluid.

The interior space of the cup 2 is exhausted through the exhaust path 245 and becomes a negative pressure, the gas above the upper surface of the wafer W (a clean air forming a downflow in the housing 11) is drawn through the gap G into the exhaust fluid path 27. Further, the N2 gas ejected from the gas ejection ports 212, 213 is flowed out of the space between the upper surface 211 of the internal peripheral portion 21 and the lower surface of the wafer W by an influence of the rotation of the wafer W, and flowed into the exhaust fluid path 27. Such flow of the gas is illustrated in FIG. 5B.

Since the lower side portion 512 of the internal peripheral surface 51 of the cover member 5 is inclined to be directed towards the radial outside as it comes close to the wafer W (that is, since the internal diameter of the lower portion of the internal peripheral surface 51 of the cover member 5 is formed so as to be larger as it goes downwardly), the gas is flowed into the gap G smoothly as compared with a case where the internal peripheral surface 51 is a single vertical surface. Accordingly, disorder of the air current hardly occurs even in the gap G. Further, a joint between the internal peripheral surface 51 of the cover member 5 and the lower surface 52 may not be made an edge (as the internal periphery 53 indicated by the reference numeral 53 in FIG. 3), but the internal peripheral surface 51 and the lower surface 52 may be made as a curved surface (see an arrow indicated by the reference numeral R in FIG. 5B). The R shape is also suitable for smoothly introducing the gas into the gap G.

Meanwhile, the chemical liquid supplied from the chemical liquid nozzle 71 to the peripheral portion of the upper surface of the wafer W and the chemical liquid supplied from the chemical liquid processing liquid ejection port 22 to the peripheral portion of the lower surface of the wafer W, are diffused towards the peripheral portion of the wafer by centrifugal force and scattered outwardly from the wafer W. Most of the chemical liquid on the upper surface of the wafer W is scattered towards a region A_(R) interposed between two arrows A₁, A₂ at the upper side in FIG. 5A. The chemical liquid is scattered the most and also the most strongly in the horizontal direction (direction of the arrow A₁), and the amount and force of the chemical liquid scattered are reduced as the scattering direction approaches a direction represented by the arrow A₂. Most of the chemical liquid on the lower surface of the wafer W is scattered towards a region B_(R) interposed between two arrows B₁, B₂ at the lower side in FIG. 5A. The chemical liquid is scattered the most and also the most strongly in the horizontal direction (direction of the arrow B₁), and the amount and power of the chemical liquid scattered are reduced as the scattering direction approaches a direction represented by the arrow B₂. As described above, the chemical liquid is scattered not only by centrifugal force, but also by an influence of the flow of the gas (clean air) that is flowed out horizontally at a gradually increasing speed when passing through the gap G between the cover member 5 and the wafer W. Meanwhile, the liquid (chemical liquid or rinse liquid) supplied to the upper surface of the wafer W does not come into contact with the lower surface 52 of the cover member 5.

The chemical liquid scattered from the wafer W flows down along the fluid receiving surface 261 and the upper surface 252 of the guide plate 25 towards the recess 241 at the outside of the cup 2, or becomes microdroplet (mist) and flows along the air current within the exhaust fluid path 27 as illustrated in FIG. 5B. The arrow illustrated as a broken line in FIG. 5B represents the air current, and the flow of the mist inside the exhaust fluid path 27 almost accords with the air current inside the exhaust fluid path 27. Meanwhile, although the liquid droplet inside the exhaust fluid path 27 proceeds through the gap G between the lower surface 52 of the cover member 5 and the upper surface of the wafer W to the central portion of the wafer W, such movement of the liquid droplet is disturbed by the above-mentioned air current that flows outwardly from the wafer W. As a result, it is possible to suppress the contamination of the wafer caused by the chemical liquid scattered from the wafer W and adhered again thereto.

In addition to the above-mentioned configuration, in order to prevent contamination of the wafer W due to the re-adhesion of the chemical liquid scattered from the wafer W, the cup 2 and the cover member 5 according to the present exemplary embodiment further include an advantageous configuration as follows.

In order to suppress bounce of the chemical liquid which is strongly incident on the fluid receiving surface 261 of the cup 2, the angle formed by the fluid receiving surface 261 of the cup 2 in relation to the horizontal surface (this is the same as the incident angle θ at which the flow of the chemical liquid indicated by the arrows A₁, B₂ is incident on the fluid receiving surface 261) is set to a relatively small value, for example, 30°. Accordingly, the scattering of the chemical liquid caused by the collision of the chemical liquid with the fluid receiving surface 261 may be reduced.

For the gap G between the lower surface 52 of the cover member 5 and the upper surface of the wafer W, an opening area (which means an area of a cylindrical surface having the same as a distance from the central axis of the cover member 5 to the internal periphery 53 of the lower surface 52, and a height G₁ (height of the gap G) of the gap G is set to be equal to or greater than an area of the exhaust port 247. Accordingly, the gas present above the upper surface of the wafer W can be drawn smoothly. If the gap G is too narrow, the flow resistance of the gap G becomes higher, and thus, sufficient exhaust cannot be achieved with a small exhaust force. The height G₁ of the gap G may be, for example, 4 mm to 5 mm.

Further, a radial width G₂ (a length in which the lower surface of the cover member 5 and the wafer W overlap in the radial direction) is about 4 mm to 6 mm, for example, 5 mm. If the width G₂ is too large, the flow resistance of the gap G becomes higher, and thus, sufficient exhaust cannot be achieved with a small exhaust force. Meanwhile, if the width G₂ is too small, it is not preferred in that the flow of the gas inside the gap G is disturbed (it is preferred that the gas inside the gap G flows horizontally towards the radial outside). Meanwhile, the optimal value of the width G₂ varies in relationship with the height G₁.

A distance D₁ between the fluid receiving surface 261 and the upper surface 252 of the guide plate 25 becomes gradually smaller as it goes downstream (as it approaches the recess 241 at the outside of the cup 2). By doing this, generation of a backflow of the air current may be prevented.

Since the cup 2 is provided with the folded portion 262, even if backflow of air current occurs as indicated by an arrow F_(R1) in FIG. 5B, the backflow is turned to the downstream side as indicated by an arrow F_(R2), by the folded portion 262. Accordingly, the mist of the chemical liquid entrained in the air current indicated by the arrow F_(R1) is suppressed from being directed to the wafer W.

Further, the height of the front end (lower end) of the folded portion 262 of the cup 2 is preferably the same as that of the lower surface 52 of the cover member 5. In this way, disorder of the gas hardly occurs when flowing through the gap G. A slight difference in height between both sides may be allowed, but, if the front end of the folded portion 262 is at a too low position, there may be a concern that the mist of the chemical liquid scattered from the surface of the wafer W (see the arrow A₂ in FIG. 5A) collides with the folded portion 262 and bounces towards the wafer W. On the other hand, if the front end of the folded portion 262 is at a too high position, it is difficult to sufficiently prevent the mist of the chemical liquid riding the air current as indicated by the arrow F_(R1) in FIG. 6 from directing towards the wafer W. Meanwhile, the distance between the peripheral portion 521 of the lower surface 52 of the cover member 5 and the folded portion 262 (distance measured in the radial direction of the wafer) is preferably as small as possible, so long as it is guaranteed that the periphery 521 does not collide with the cup 2 when the cover member 5 is moved up. As a result, the gas that has passed through the gap G is prevented from forming turbulence in the space between the periphery 521 and the folded portion 262.

When the cover member 5 is located at the processing position, it is preferred that the space between the cover member 5 and the upper surface of the external peripheral wall 25 is sealed by a seal member 59, as illustrated in FIG. 3. Accordingly, since the gas inside the housing 11 is introduced solely through the gap G into the exhaust fluid path 27, disorder of the air current hardly occurs in the vicinity of the external periphery of the wafer W, and a load on the exhaust apparatus 246 may be reduced as well.

Meanwhile, the flows of air current and mist in the chemical liquid processing have been described above. However, it is evident that the flows of air current and mist are also generated similarly in the rinse processing.

The liquid processing performed by the liquid processing apparatus 1 is not limited to the foregoing. For example, the chemical liquid is not limited to HF, but may be SC-1 or SC-2. Further, the chemical liquid processing may be performed several times. In addition, the substrate to be processed is not limited to a semiconductor wafer, but may be various circular substrates of which the peripheral portion is required to be cleaned, for example, a glass substrate and a ceramic substrate.

From the foregoing, it will be appreciated that various embodiments of the present disclosure have been described herein for purposes of illustration, and that various modifications may be made without departing from the scope and spirit of the present disclosure. Accordingly, the various embodiments disclosed herein are not intended to be limiting, with the true scope and spirit being indicated by the following claims. 

What is claimed is:
 1. A substrate processing apparatus comprising: a substrate holding unit configured to hold a substrate horizontally; a rotation driving mechanism configured to rotate the substrate holding unit around a vertical axis; a processing liquid nozzle configured to supply a processing liquid to a peripheral portion of the substrate held by the substrate holding unit; a cup configured to receive the processing liquid scattered outwardly from the substrate, the cup having an upper opening and enclosing the periphery of the substrate held by the substrate holding unit; an exhaust port configured to exhaust the interior space of the cup; and a ring-shaped cover member having a lower surface and an internal peripheral surface, wherein the cover member covers the peripheral portion of the upper surface of the substrate held by the substrate holding unit, a central portion of the substrate located at an inner position than the peripheral portion in a radial direction is exposed without being covered by the cover member, and a gap is formed between the lower surface of the cover member and the peripheral portion of the upper surface of the substrate held by the substrate holding unit, and when the interior space of the cup is exhausted, a gas present above the interior space of the cup is introduced from a space enclosed by the internal peripheral surface of the cover member through the gap into the interior space of the cup.
 2. The substrate processing apparatus of claim 1, wherein an internal diameter of the lower portion of the internal peripheral surface of the cover member becomes larger as it goes downwardly.
 3. The substrate processing apparatus of claim 2, wherein a lower end of the internal peripheral portion and an internal peripheral portion of the lower surface in the cover member are connected to each other so as to be a curved surface.
 4. The substrate processing apparatus of claim 1, wherein an internal periphery of the lower surface of the cover member is located at an inner position than an external peripheral end of the substrate held by the substrate holding unit, and an external periphery of the lower surface of the cover member is located at an outer position than an external periphery of the substrate held by the substrate holding unit.
 5. The substrate processing apparatus of claim 4, wherein the internal periphery of the lower surface of the cover member is located at an inner position than an internal periphery of the peripheral portion of the substrate held by the substrate holding unit.
 6. The substrate processing apparatus of claim 1, wherein an opening area of the gap is larger than that of the exhaust port.
 7. The substrate processing apparatus of claim 1, wherein the cup has an upper opening into which the lower portion of the cover member is inserted, and a wall that defines the upper opening of the cup is provided with a folded portion that extends downwardly.
 8. The substrate processing apparatus of claim 1, further comprising a moving mechanism configured to move the cover member between a processing position that comes close to the upper surface of the substrate held by the substrate holding unit and a retreat position apart from the substrate. 